The kidney is the major erythropoietin-producing organ; decreased erythropoietin production accompanying renal failure causes renal anemia as a complication.
In recent years, as next-generation therapeutic methods for renal anemia as such, methods have been proposed wherein an artificial kidney possessing a potential for erythropoietin production or a precursor thereof is produced by regenerative medical technology, and this is transplanted to renal anemia patients. For example, Patent Document 1 discloses a method for producing erythropoietin-producing organoid (artificial kidney) precursor comprising the step of transplanting isolated mesenchymal stem cell derived from a mammal into an embryo within a pregnant mammalian host or an embryo separated from a pregnant mammalian host to thereby induce the differentiation of the mesenchymal stem cell, wherein a site to which the mesenchymal stem cell is to be transplanted is a nephrogenic site of the embryo, and a timing of transplantation corresponds to the stage in which a immune system of the host is still immunologically tolerant.
In this method, however, there is a problem of complicated process because it is necessary to collect amniotic fluid from a pregnant mammal just before the artificial kidney precursor is transplanted to the patient, and confirm the biological safety of the precursor. Additionally, mesenchymal stem cells must be injected into an appropriate site in the embryo, that can become the kidney in the future; this operation requires high skills. Additionally, because mesenchymal stem cells must be injected into the embryo while the host's immune system is in a state of immune tolerance, the flexibility of the entire schedule of treatment is low. In this method, it is difficult to obtain a functional artificial kidney precursor unless whole embryo culture is performed; there arises a risk of contamination due to cultivation, and complicated process of purification after cultivation is necessary.
Hence, there is a demand for the development of a method of producing an artificial kidney precursor wherein 1) the biological safety of the artificial kidney precursor can easily be tested before transplantation to the patient, 2) the operation is simple, 3) flexibility of the entire schedule of treatment can be secured, and 4) no operation of cultivation is required.